My advised to you is: Each time you want to buy a computer or hardware always make a choice depend your budget. And tell people about your budget. It'll make easier for people to suggest best bang for buck stuff

Uh, I'd reccommend i7 on a laptop personally, I don't do much multitasking but I often find I'm using 4 or 8 threads with hefty programs...I think in the future it'll become more and more common for programs to use lots of threads. And for Sims 3, any i series laptop with any dedicated graphics card should be fine, even shared would probably be okay!